1. Field of the Invention
The present invention relates to an airbag device for use in a vehicle such as an automobile to protect passengers sitting at the front seat, the driver seat, or the seats at both the left and right side columns from any potential impact in an accident, thus proving more safety, and more particularly, it relates to the improvement in a fracture-opening section for use in inflating an airbag element, formed in an interior cover, in order to facilitate breakage of the cover.
2. Description of the Related Art
An airbag device for use in a vehicle such as an automobile installed at a driver seat, a passenger seat and left or right side columns basically comprises an airbag element, an airbag case accommodating the airbag element in its folded form and an inflator for inflating the airbag element, and is covered by an interior cover of the vehicle.
Furthermore, an interior cover of an automobile generally comprises an instrument panel cover made of synthetic resin such as polypropylene (hereinafter referred to an “interior cover”) which covers a panel core made of molded form of synthetic resin such as polypropylene.
A conventional passenger-side airbag device 1, as shown in FIGS. 1 and 2, is installed on the horizontal surface of 3a of an interior cover 3 near a windshield 1a, accommodates an airbag element 4 in its folded form which will inflate by supplying a flow of gas from the inflator, and contains an airbag case 5 having an opening 5a opposite the rear surface of the interior cover 3, wherein an open lid 6 molded of flexible synthetic resin is mounted in an opening 3b formed in the interior cover 3, and the open lid 6 is separated apart in the forward and rearward directions by breaking off into two parts at grooves 6a, 6b formed in the center and periphery of the open lid 6 when an airbag element 4 inflates.
Then, on the rear surface of the open lid 6 are mounted mounting legs 7 having a rectangular shape in the horizontal cross section which is molded as a single unit having a slightly larger periphery than that of the opening 5a of the case 5, and a plurality of joiners 8 to engage elastically with the opening circumference of the opening 3b formed in the interior cover 3. And furthermore, a plurality of angular through holes 7c are formed on the front and rear wall surfaces 7a, 7b of the mounting legs 7, which are engaged with a plurality of hooks 9 mounted to the front and rear wall surfaces 5b, 5b of the opening 5a of the case 5, when the open lid 6 is attached to the opening 3b formed in the interior cover 3.
Here, when the airbag element 4 inflates, the open lid 6 breaks off the front and rear sections at the position of the grooves 6a, 6b formed at its periphery and center, and after the inflation of the airbag element, a plurality of angular holes 7c in the front and rear wall surfaces 7a, 7b of the mounting leg 7 remain engaged with the hooks 9 which are mounted to the front and rear wall surfaces 5b, 5b of the opening 5a of the case 5, hence preventing the open lid 6 from generating sharp edges of scattering broken pieces.
However, in the passenger-side airbag device as shown in FIG. 1, it is constructed such that the opening 3b in the interior cover 3 is formed in the position corresponding to the opening 5a in the airbag case 5, and further, the open lid 6 is mounted, which is engaged with this opening 3b and separately formed of flexible resin material different from that of the interior cover 3. Accordingly, there are still some troublesome problems to manufacture it, and the open lid 6 can be easily deformed against an external pressure, resulting in damaging the appearance or design of the interior cover.
Also, there might be another problem permitting the open lid 6 to pop out, because there is no reinforcement cover mounted on the back side of the open lid 6 in the separately formed open lid 6 and the engagement between the mounting legs 7 of the open lid 6, and the hooks 9 mounted to the forward and rear wall surfaces 5b, 5b of the opening 5a of the airbag case 5 can be easily separated because the engagement is made of flexible resin upon the inflation of the airbag element 4.
Accordingly, in order to overcome these problems as mentioned above, the present applicant proposed a seamless type passenger-side airbag system by our prior Patent Application No. 2000-20238 (filed on Jan. 28, 2000,), where the separately formed open lid is not used, and consequently no line appears in the interior cover.
FIG. 3 is a partial enlarged view showing that a fracture-opening section 30 for inflating the airbag is formed in a single plate shaped interior cover 3 of a passenger-side airbag device. FIG. 4 is a schematic cross-sectional view taken along the line 4B—4B in FIG. 3. FIG. 5 is an explanatory view showing the device with fracture-opening section 30 removed from the interior panel 3. FIG. 6 is an enlarged cross-sectional view taken along the arrow C in FIG. 5.
In FIGS. 3 and 4, in the interior cover 3, the fracture-opening section 30 for use upon the inflating of the airbag element is formed corresponding to the size of the opening 5a in the airbag case 5, by forming hinge grooves 30a, grooves 30b, 30c extending circumferentially in a dotted line or a broken line with a pulsating laser beam from a laser generating device (not shown) which releatively moves from the back side of the interior cover 3 along the external margins of reinforcement plates 10, 10, mounted to the back side of the interior cover. In addition, when the airbag element inflates, it breaks the fracture-opening section 30 lifting up the groove 30b formed therein into leftward and rightward longer directions in a way like a double-door opening outward.
This prior application provides the airbag device for automobiles constructed such that the fracture-opening section 30 in the interior cover 3 is separated from the interior cover 3 by the airbag element 4 when it inflates, and one end of the level surface of the reinforcement plates 10, 10, respectively is mounted to the back side of fracture-opening section 30 of the interior cover 3 by thermal bonding, while the other end thereof is allowed to hang at the rear surface of the interior cover 3 via hinges 11, 11 and engaged with a pair of reinforcement ribs 12 having distances slightly wider than the width of the opening 5a in the airbag case 5. With this construction, it has improved the drawbacks existing in the prior art with an open lid 6 constructed separately, hence reducing a force of impact onto a passenger when the vehicle or automobile is involved in a collision, preventing the fracture-opening section 30 of the interior cover 3 lifting up like double doors opening outward from popping out when the airbag element inflates, and further protecting the chest and head of passenger seated on the front seat from any potential danger.
Sections 13 is the thinned portion formed at the rear connecting portion in the interior cover 3 of a pair of reinforcement ribs 12. As the airbag elements is instantly inflated, it breaks down the thinned portion at the rear connecting portion of the interior cover 3 and abruptly lifts up the fracture-opening section 30 of the interior cover 3.
In the airbag device for automobiles constructed as described above, when the automobile is involved in a collision, its degree is detected by a sensor(s), which in turn is judged by a control device like a CPU, whether or not it is over the predetermined value, and in case the value is judged as “over the predetermined value”, a signal output from the control device causes the inflator to generate a certain amount of gas.
The pressure for inflating the airbag element acts on the inside surface of the fracture-opening section 30 of the interior cover 3, causing the fracture-opening section to break along the grooves 30b, 30c, and separate from the interior cover 3, and then this separated fracture-opening section 30 can be opened outside of the interior cover 3 by fulcruming each hinge 11 of the reinforcement plate 10, 10 respectively.
At the same time, the airbag element 4 inflates outside of the interior cover 3 from the opened fracture-opening section 30, hence preventing the passenger from the impact from a collision of the vehicle by supporting the chests, heads, arms or legs of passengers seated on the driver seat, the passenger seat, and seats at both the left and right side columns.
However, there are still other drawbacks in the improved interior cover 3, and the fracture-opening section 30 has some detects in its safety as mentioned below. In the interior cover 3 of the prior improved device, hinge grooves 30a, the fracture grooves 30b, 30c are formed, penetrating at a right angle from the backside toward the front of the interior cover 3, and the reinforcement plates 10a, 10a bent by the hinges 11 along the longer direction of each of left and right sides of the fracture-opening section 30 are thermally bonded in place, respectively, and then, the other ends of the reinforcement plates 10, 10 are engaged with respectively a pair of front and rear reinforcement ribs 12, 12 protruding in the longer direction from leftward to rightward) of the fracture-opening section 30, so that in the front and rear fracture grooves 30a in the longer direction (from leftward to rightward) of the fracture-opening section 30, or in the central fracture groove 3b of the fracture-opening section 30, a fracture surface does not have any serious problems in its fracture shape when the airbag element inflates, while, since the fracture of the left and right fracture grooves 30c in the shorter direction (from forward to backward) has no hinges for the reinforcement ribs 12, 12 and the reinforcement plates 10, 10 the device is structurally weak in the fracture in frontward-rearward shorter directions of fracture-opening section 30 and the fracture surface becomes serrate. In particular, under such severe weather conditions where the temperature inside the car can rise to as high as +75° C. in summer and drop to −35° C. in winter, as shown in FIG. 6, a shearing force would act to cause sharp edges 3c to occur on the fracture surface.